The present invention relates to realtime spectrum analysis, and more particularly to a realtime power mask trigger for acquiring signal data in realtime.
Several spectrum analyzers on the market currently have a frequency mask trigger function, which analyzers include the Tektronix WCA200, WCA300, RSA2200 and RSA3300 series realtime spectrum analyzers. These analyzers capture and analyze seamless blocks of data so that, unlike conventional swept frequency analyzers, no data is missed or lost. One function that is performed in real time is a frequency mask trigger function, as illustrated in FIG. 1. In the case of the WCA200 this trigger is implemented with a dedicated FFT processor that calculates the signal spectrum on the realtime data provided by its receiver system. When the calculated spectrum violates a user-defined spectrum (frequency) mask, a predefined block of data is stored covering information on what happened immediately after (post-trigger) and before (pre-trigger) the triggering event. The frequency mask trigger works by comparing the amplitude of each frequency bin in the calculated signal spectrum to the user-defined spectral mask. In this manner the analyzer waits for a specific event to occur.
However there are instances where events occur that are buried in the spectral noise floor of the signal or frequency range being monitored. In this situation the amplitude of any particular frequency bin does not exceed the user-defined frequency mask, although an event still may cause interference with a particular signal being monitored or may indicate a noise-like, stealthy signal.
What is desired is a method of detecting events in the spectrum of a frequency range of interest that is buried in the noise floor of the signal spectrum.